In the context of the measurement of the visual acuity of a patient, it has already been proposed to simulate the visual compensation to be provided, for example by means of trial spectacles or a refractor such as a refraction head.
In the refraction head, trial lenses are placed on a plurality of discs that are rotated manually or using a motorized mechanism. However, it will be understood that such an object has a substantial bulk and weight related to the number of lenses placed on each disk.
Trial spectacles are less bulky. Provision is indeed made for them to successively receive trial lenses having different corrections, until the correction which is appropriate for the patient is found.
This solution is however rather impractical, particularly because it requires separate storage of the trial lenses in dedicated boxes. It furthermore involves lens changes, resulting in undesired and non-continuous transitions in corrective power.